Underground cables can be laid alongside motorways/roads and can be placed in ducts or tunnels underneath them. Cables can be buried directly along the side of motorways/roads with only partial impact on the traffic (e.g. dedicated lane). The motorway crossing may be realised by directional drilling, pipe jacking or micro tunnelling and will depend on the technique most appropriate to the particular site.
When installing cables, it is possible to cross rivers using bridges, installing the cables under the river bed (using directional drilling) or by installing the cables in ducts placed on or in the river bed. Disturbance of river beds and water flow to fish and other species can therefore be minimized and the use of XLPE insulated cables removes any risk of damage to the surrounding environment from leaks.
As explained in the recent CIGRE paper5 into the recently installed UGC between Turbigo and Rho in Italy, cables were laid underneath roads and under two rivers. Under the roadway, cables were laid in PVC pipes blocked by concrete and for the river crossings, the cables were laid in polyethylene pipes that were filled with water to improve heat dispersion.
The presence of other pipelines and cables is something faced on a regular basis by cable installers, particularly in urban areas. Existing trenches containing oil/gas pipelines should not represent any significant barrier and might be advantage in that rights of way have already been agreed. The minimum clearance to be observed between a gas pipeline and a power cable would usually be determined by the gas transportation company and would depend on the diameter of the pipe and the gas pressure.